How does The Bird-nest Incubation Unit Work?

Abstract

The bird-nest incubation unit was proposed as a means of explaining the functionality of incubation in most avian species where the egg is in direct contact with the incubator. Subsequent work resulted in revision of this idea to suggest that large birds act as incubators and the nest is a location for incubation; by contrast, in small species the interaction between the bird and its nest played a key role in ensuring efficiency of incubation. Thispaper briefly reviews what we know about the incubation environment within nests and considers how small birds can contact-incubate eggs whilst ensuring appropriate levels of respiratory gas exchange. A hypothesis is proposed that the incubating bird does not 'sit tight' on its nest to maintain egg temperature at a minimal energy expenditure but, rather, it allows warmed air to escape from the nest cup. This convection flow draws air into the cup from the nest walls, providing oxygen for developing eggs and diluting carbon dioxide that they produce. Evidence supporting this idea of an 'open' nest during incubation is presented. Further experimentation is required to understand the environment within the nest cup better and this paper presents a hypothesis that can be tested in future studies. Investigations of how nests interact with their immediate environment should no longer be biased towards the effects of temperature on nest dimensions or composition. Instead, they should address all of the environmental factors that could affect the composition and function of a bird nest.

Birds use structural properties when selecting materials for different parts of their nests

“…Whilst the nest itself is primarily where eggs are incubated (Deeming 2016) it is suggested that they have a range of other roles associated with reproduction, and perhaps even lifetime fitness (Moreno 2012;Mainwaring et al 2014a). Birds select materials during nest construction for a variety of reasons (Deeming and Mainwaring 2015), including sexual signalling (Dubiec et al 2013;Tomás et al 2013), defence from parasites or pathogens (Dubiec et al 2013), camouflage (Kull 1977;Bailey et al 2015), insulation (Hilton et al 2004;Dhandhukia and Patel 2012;Mainwaring et al 2014b) or for their structural role (Bailey et al 2014;Biddle et al 2015Biddle et al , 2017.…”

bwimage: A package to describe image patterns in natural structures

“…Variation in eggs and nest morphology provide relevant information concerning bird life history that has frequently been used to answer ecological [10][11][12] and evolutionary questions [13][14][15] . Here we analyze examples that address the quantification nest wall openness and the aggregation of nest wall holes, using a nest of the blueblack grasssquit (Volatinia jacarina) deposited in the museum collection Coleção Ornitológica Marcelo Bagno, at Universidade de Brasília (register number COMB-N682).…”

bwimage: A package to describe image patterns in natural structures

“…A photograph of the portion of standing vegetation against the white cloth was taken. Variation in eggs and nest morphology provide relevant information concerning bird life history that has frequently been used to answer ecological [10][11][12] and evolutionary questions [13][14][15] . Here we analyze examples that address the quantification nest wall openness and the aggregation of nest wall holes, using a nest of the blueblack grasssquit (Volatinia jacarina) deposited in the museum collection Coleção Ornitológica Marcelo Bagno, at Universidade de Brasília (register number COMB-N682).…”